For example, JPH09-166238A teaches a solenoid valve, which serves as a pressure control valve. With reference to FIG. 15, the solenoid valve of JPH09-166238A includes a spool 110, which is received in a sleeve 100 and is reciprocatable in an axial direction. A spring 120 urges the spool 110 toward a side (the right side in FIG. 15) against a drive force of a solenoid device (drive device). The solenoid valve further includes an adjust screw 130. With reference to FIG. 16, a male-threaded portion 130a is formed in an outer peripheral surface of the adjust screw 130 and is engaged with a female-threaded portion 100a of the sleeve 100, which is formed in one end part of an inner peripheral surface of the sleeve 100. A set load of the spring 120 is adjusted by adjusting the amount of insertion of the adjust screw 130 into the sleeve 100.
A rotational force is applied to the adjust screw 130 from a jig (not shown) to adjust the set load of the spring 120. Thereafter, a pin 140 (see FIG. 18) is inserted into a through-hole 101, which radially extends through a peripheral wall of the sleeve 100, to plastically deform a crest 130ac of the male-threaded portion 130a of the adjust screw 130 in a radially inner direction. When the crest 130ac of the male-threaded portion 130a is plastically deformed, i.e., compressed in the radially inner direction by the pin 140, rotation of the adjust screw 130 is limited to fasten the adjust screw 130 in place. Thereby, the installation position of the adjust screw 130 is fixed.
Hereinafter, the step of adjusting the set load of the spring 120 through application of the rotational force to the adjust screw 130 with the jig will be referred to as a pressure adjusting step.
JP2011-33181A teaches another technique. Specifically, with reference to FIGS. 20 and 21, a sealing material is filled in a space located on a rear side of the adjust screw 130, which is opposite from the spring 120 in the axial direction. When the sealing material is solidified, loosening of the adjust screw 130 is limited.
When the pressure adjusting step is executed, the adjust screw 130 receives an axial load F1 of the jig, which applies the rotational force to the adjust screw 130, and a reaction force F2 of the spring 120.
With reference to FIG. 16, the female-threaded portion 100a of the sleeve 100 has a first flank 100a1 and a second flank 100a2. The first flank 100a1 is located on one side of a crest 100ac of the female-threaded portion 100a, which is opposite from the spring 120 in the axial direction. The second flank 100a2 is located on the other side of the crest 100ac of the female-threaded portion 100a, which is opposite from the one side of the crest 100ac of the female-threaded portion 100a in the axial direction. Furthermore, the male-threaded portion 130a of the adjust screw 130 has a first flank 130a1 and a second flank 130a2. The first flank 130a1 is located on one side of a crest 130ac of the male-threaded portion 130a, which is opposite from the spring 120 in the axial direction. The second flank 130a2 is located on the other side of the crest 130ac of the male-threaded portion 130a, which is opposite from the one side of the crest 130ac of the male-threaded portion 130a in the axial direction. Normally, the pressure adjusting step is executed in a state where a condition of F1>F2 is satisfied. In this state, as shown in FIG. 17A, the adjust screw 130 is urged toward the spring 120, and thereby the second flank 130a2 of the male-threaded portion 130a contacts the first flank 100a1 of the female-threaded portion 100a on the spring 120 side of the crest 130ac of the male-threaded portion 130a. Furthermore, a pitch clearance is formed between the first flank 130a1 of the male-threaded portion 130a and the second flank 100a2 of the female-threaded portion 100a on the opposite side of the crest 130ac of the male-threaded portion 130a, which is opposite from the spring 120 side in the axial direction.
Thereafter (i.e., after the execution of the pressure adjusting step), when the axial load F1 of the jig applied against the adjust screw 130 is removed, the adjust screw 130 is moved toward the left side (the opposite side, which is opposite from the spring 120 in the axial direction) by the reaction force of the spring 120. That is, the position of the adjust screw 130 relative to the sleeve 100 is deviated toward the opposite side, which is opposite from the spring 120 in the axial direction. Therefore, the first flank 130a1 of the male-threaded portion 130a contacts the second flank 100a2 of the female-threaded portion 100a on the opposite side of the crest 130ac, which is opposite from the spring 120 side in the axial direction. Furthermore, a pitch clearance is formed between the second flank 130a2 of the male-threaded portion 130a and the first flank 100a1 of the female-threaded portion 100a on the spring 120 side of the crest 130ac of the male-threaded portion 130a. When the crest 130ac of the male-threaded portion 130a of the adjust screw 130 is plastically deformed in the radially inner direction by the pin 140, the adjust screw 130 may be fastened in the state where the position of the adjust screw 130 is deviated from its preset position relative to the sleeve 100 in the axial direction. Therefore, in such a case, the set load of the spring 120 is changed to cause the pressure adjustment deviation.
Specifically, at the time of plastically deforming the crest 130ac of the male-threaded portion 130a of the adjust screw 130 with the pin 140, an axial force component f1 of the plastically deforming force is applied from the pin 140 to the first flank 130a1 located on the opposite side of the crest 130ac, which is opposite from the spring 120 side in the axial direction, and an axial force component f2 of the plastically deforming force is applied from the pin 140 to the second flank 130a2 located on the spring 120 side of the crest 130ac. The relationship between the axial force component f1 and the axial force component f2 will be one of f1>f2 and f1<f2 depending on the axial position of the adjust screw 130 relative to the pin 140. That is, at the time of plastically deforming the crest 130ac of the male-threaded portion 130a of the adjust screw 130 in the radially inward direction with the pin 140, when the axial force component f1, which is applied from the pin 140 to the first flank 130a1 of the male-threaded portion 130a, is smaller than the axial force component f2 of the plastically deforming force, which is applied from the pin 140 to the second flank 130a2 of the male-threaded portion 130a (i.e., f1<f2), as shown in FIG. 18, the adjust screw 130 is fastened to the sleeve 100 in the state (i.e., the state of FIG. 17B) where the first flank 130a1 of the male-threaded portion 130a contacts the second flank 100a2 of the female-threaded portion 100a on the opposite side of the crest 130ac, which is opposite from the spring 120 side in the axial direction. Therefore, the set load of the spring 120 is changed by the amount, which corresponds to the pitch clearance, thereby resulting in the pressure adjustment deviation.
In contrast, when the axial force component f1, which is applied from the pin 140 to the first flank 130a1 of the male-threaded portion 130a, is larger than the axial force component f2 of the plastically deforming force, which is applied from the pin 140 to the second flank 130a2 of the male-threaded portion 130a (i.e., f1>f2), as shown in FIG. 19, the adjust screw 130 is moved toward the spring 120 side (the side where the pitch clearance is formed). At this time, the amount of displacement of the adjust screw 130 cannot be accurately controlled. In other words, the amount of displacement of the adjust screw 130 changes depending on the axial force components f1, f2 of the plastically deforming force. Therefore, the axial positional deviation of the adjust screw 130 cannot be reliably limited. Therefore, the set load of the spring 120 is changed to cause the pressure adjustment deviation.
Furthermore, according to the technique of JP2011-33181A, when the jig is removed to fill the seal material in the space located on the rear side of the adjust screw 130 (the side opposite from the spring 120 in the axial direction) after the execution of the pressure adjusting step, the adjust screw 130 is urged backward by the reaction force of the spring 120, as shown in FIG. 20. Therefore, the first flank 130a1 of the male-threaded portion 130a of the adjust screw 130 contacts the second flank 100a2 of the female-threaded portion 100a of the sleeve 100 on the opposite side of the crest 130ac of the male-threaded portion 130a, which is opposite from the spring 120 side in the axial direction, and the pitch clearance is formed between the second flank 130a2 of the male-threaded portion 130a and the first flank 100a1 of the female-threaded portion 100a on the spring 120 side of the crest 130ac of the male-threaded portion 130a. Thereafter, when the seal material is filled in the space located on the rear side of the adjust screw 130, the filling pressure of the seal material is applied to the rear surface of the adjust screw 130. Therefore, as shown in FIG. 21, the adjust screw 130 is moved toward the spring 120 side. However, the amount of displacement of the adjust screw 130 may vary. Therefore, in such a case, the pressure adjustment deviation may occur.
As discussed above, in the techniques of JPH09-166238A and JP2011-33181A, the adjust screw 130 may possibly be displaced in the axial direction by the amount, which corresponds to the pitch clearance, at the time of fixing the installation position of the adjust screw 130 relative to the sleeve 100 (i.e., at the time of limiting the rotation of the adjust screw 130 relative to the sleeve 100) after the execution of the pressure adjusting step. Therefore, the accurate adjustment of the set load of the spring 120 is difficult.